Recording of information from gaseous discharge display memory panel

ABSTRACT

THERE IS DISCLOSED THE GENERATING AND RECORDING OF IMAGE INFORMATION FROM A MULTIPLE GASEOUS DISCHARGE DISPLAY/MEMORY PANEL HAVING AN ELECTRICAL MEMORY AND CAPABLE OF SIMULTANEOUSLY PRODUCING INFORMATION IN THE FORM OF A VISUAL OR LATENT IMAGE, THE PANEL BEING FURTHER CHARACTERIZED BY AN IONIZABLE GASEOUS MEDIUM IN A GAS CHAMBER FORMED BY A PAIR OF OPPOSED DIELECTRIC MATERIAL CHARGE STORAGE MEMBERS WHICH ARE RESPECTIVELY BACKED BY A SERIES OF PARALLEL-LIKE CONDUCTOR (ELECTRODE) MEMBERS, THE CONDUCTOR MEMBERS BEHIND EACH DIELECTRIC MATERIAL MEMBER BEING TRANSVERSELY ORIENTED WITH RESPECT TO THE CONDUCTOR MEMBERS BEHIND THE OPPOSING DIELECTRIC MATERIAL MEMBER SO AS TO DEFINE A PLURALITY OF DISCRETE DISCHARGE VOLUMES, EACH OF WHICH CONSTITUTES A DISCHARGE UNIT, THE VISUAL OR LATENT IMAGE BEING COMPRISED OF ONE OR MORE DISCHARGE UNITS, AND IMAGE RADIATION FROM THE DISCHARGE UNITS BEING PROJECTED ONTO A PHOTOSENSITIVE SURFACE ADAPTED TO RECEIVE AND RECORD THE IMAGE. THE PROJECTED IMAGE RADIATION MAY BE VISIBLE OR LATENT (INVISIBLE) RELATIVE TO THE HUMAN EYE.

- [111 3,821,748 [4 June 28, 1974 Primary Examiner-Bemard KonickAssistant Eraminer-Jay P. Lucas Attorney, Agent, or Firm-Donald KeithWedding [57] ABSTRACT There is disclosed the generating and recording ofimage information from a multiple gaseous discharge display/memory panelhaving an electrical memory and capable of simultaneously producinginformation in the form of a visual or latent image, the panel beingfurther characterized by an ionizable gaseous medium in a gas chamberformed by a pair of opposed dielectric material charge storage memberswhich are respectively backed by a series of parallel-like conductor(electrode) members, the conductor members behind each dielectricmaterial member being transversely oriented with respect to theconductor members behind the opposing dielectric material member so asto define a plurality of discrete dischar umes, each of whichconstitutes a dischar visual or latent imagebeing com RECORDING OFINFORMATION FROM GASEOUS DISCHARGE DISPLAY/MEMORY PANEL Inventor: FelixH. Brown, East Lansing, Mich.

Assignee: Owens-Illinois, Inc., Toledo, Ohio Dec. 23, 1970 Appl. No.:101,102

US. 346/74 P, 340/173 PL HOlj 17/48, H lj 61/33, Hb 41/44 Field ofSearch 346/74 ES, 74 P; 355/3,

355/5, 307/88 ET; 340/173 PL References Cited UNITED STATES PATENTSUnited States Patent Brown [22] Filed:

[51] lnt.Cl...

ee 6. V m ST( C w fl mrl Ve u m gm 6 m n nm 0 a m d mk d m b m pas i w rp 340/334 /45 346/74 P 340/324 95/4.5 X discharge units, and imageradiation from the dis 95/4.5 X charge units being projected onto a340/173 fac e adapted to receive and reco projected image radiation maybe visible) relative to the human eye.

.. 307/88 ET I 307/88 ET 340/173 PL M fm m m. nr fi mmm m mO Lfr. mrn eeO .w.w 630 Ca LKCDTBOO 2356800000 6666667777 9999999999 HHHHHHHHHH 2286936 12 lCllaims, 5 Drawing Figures SHEU E OF PAIENTEMuxzs 1974RECORDING OF INFORMATION FROM GASEOUS DISCHARGE DISPLAY/MEMORY PANEL THEINVENTION This invention relates to novel multiple gas dischargedisplay/memory panels which have an electrical memory and which arecapable of producing a visual image display or a latent image, e.g. arepresentation of data such as numerals, letters, television display,radar displays, binary words, etc. More particularly, this inventionrelates to the generating and recording of.visual or latent informationfrom a gas discharge display/memory panel.

Multiple gas discharge display and/or memory panels of the type withwhich the present invention is concerned are characterized by anionizable gaseous medium, usually a mixture of at least two gases at anappropriate gas pressure, in a thin gas chamber or space between a pairof opposed dielectric charge storage members which are backed byconductor (electrode) members, the conductor members backing eachdielectric member being transversely oriented to define a plurality ofdiscrete discharge volumes, each of which constitutes a discharge unit.In some prior art panels the discharge units are additionally defined bysurrounding or confining physical structure such as by cells orapertures in perforated glass plates and the like so as to be physicallyisolated relative to other units. In either case, with or without theconfining physical structure, charges (electrons, ions) produced uponionization of the gas of a selected discharge unit, when properalternating operating potentials are applied to selected conductorsthereof, are collected upon the surfaces of the dielectric atspecifically defined locations and constitute an electrical fieldopposing the electrical field which created them so as to terminate thedischarge for the remainder of the half cycle and aid in the initiationof a discharge on a succeeding opposite half cycle of applied voltage,such charges as are stored constituting an electrical memory.

Thus, the dielectric layers prevent the passage of any conductivecurrent from the conductor members to the gaseous medium and also serveas collecting surfaces for ionized gaseous medium charges (electrons,ions) during the alternate half cycles of the AC. operating potentials,such charges collecting first on one elemental or discrete dielectricsurface area and then on an opposing elemental or discrete dielectricsurface area on alternate half cycles to constitute an electricalmemory.

An example of a panel structure containing nonphysically isolated oropen discharge units is disclosed in US. Letters Patent 3,499,] 67issued to Theodore C. Baker et al.

An example of a panel containing physically isolated units is disclosedin the article by D; L. Bitzer and H. G. Slottow entitled The PlasmaDisplay Panel A Digitally Addressable Display With Inherent Memory,Proceeding of the Fall Joint Computer Conference, IEEE, San Francisco,California, Nov. 1966, pages 541-547.

ln the operation of the panel, a continuous volume of ionizable gas isconfined between a pair of dielectric surfaces backed by conductorarrays forming matrix elements. The cross conductor arrays may beorthogonally related (but any other configuration of conductor arraysmay be used) to define a plurality of opposed pairs of charge storageareas on the surfaces of the dielectric bounding or confining the gas.Thus, for a conductor matrix having H rows and C columns the number ofelemental discharge volumes will be the product H X C and the number ofelemental or discrete areas will be twice the number of elementaldischarge volumes.

The gas is one which produces light (if visual display is an objective)and a copious supply of charges (ions and electrons) during discharge.In an open cell Baker, et al. type panel, the gas pressure and theelectric field are sufficient to laterally confine charges generated ondischarge within elemental or discrete volumes of gas between opposedpairs of elemental or discrete dielectric areas within the perimeter ofsuch areas, especially in a panel containing non-isolated units.

As described in the Baker et al. patent, the space between thedielectric surfaces occupied by the gas is such as to permit photonsgenerated on discharge in a selected discrete or elemental volume of gasto pass freely through the gas space and strike surface areas ofdielectric remote from the selected discrete volumes, such remote,photon struck dielectric surface areas thereby emitting electrons soasto condition other and more remote elemental volumes for discharges at auniform applied potential.

With respect to the memory function of a given discharge panel, theallowable distance or spacing between the dielectric surface depends,inter valia, on the frequency of the alternating current supply, thedistance typically being greater for lower frequencies.

While the prior art does disclose gaseous discharge devices havingexternally positioned electrodes for initiating a gaseousdischarge,'sometimes called electrodeless discharges, such prior artdevices utilize frequencies and spacings of discharge volumes andoperating pressures such that although discharges are initiated in thegaseous medium, such discharges are ineffective or not utilized forcharge generation and storage in the manner of the present invention.

The term memory margin is defined herein as where V, is the magnitude ofthe applied voltage at which a discharge is initiated in a discreteconditioned (as explained in the aforementioned Baker, et al. patent)volume of gas defined by common areas of overlapping conductors and V isthe magnitude of the minimum applied periodic alternating voltagesufficient to sustain discharges once initiated. It will be understoodthat basic electric phenomena utilized in this invention is thegeneration of charges (ions and electrons) alternately storable at pairsof opposed or facing discrete points or areas on a pair of dielectricsurfaces backed by conductors connected to a source of operatingpotential. Such stored charges result in an electrical field opposingthe field produced by the applied potential that created them and henceoperate to terminate ionization in the elemental gas volume betweenopposed or facing discrete points or areas of dielectric surface. Theterm sustain a discharge means producing a sequence of momentarydischarges, one discharge for each half cycle of applied alternatingsustaining voltage, once the elemental gas volume has been fired, to

maintain alternate storing of charges at pairs of opposed discrete areason the dielectric surfaces.

The features and advantages of the invention will be better understoodby reference to the following detailed description when considered inconnection with the accompanying drawings. FIGS. 1 4 and the descriptionof these figures are from the above mentioned Baker et al. US. Pat. No.3,499,167.

FIG. 1 is a partially cut-away plan view of a gaseous display/memorypanel as connected to a diagrammatically illustrated source of operatingpotentials,

FIG. 2 is a cross-sectional view (enlarged, but not to proportionalscale since the thickness of the gas volume, dielectric members andconductor arrays have been enlarged for purposes of illustration) takenon the lines 22 of FIG. 1,

FIG. 3 is an explanatory partial cross-sectional view similar to FIG. 1(enlarged, but not to proportional scale),

FIG. 4 is an isometric view of a larger gaseous discharge display/memorypanel, and

FIG. 5 is a diagrammatic view of the combination of the gaseousdischarge display/memory panel and a photosensitive element of arecording device.

The invention utilizes a pair of dielectric films or coatings and 11separated by a thin layer or volume of a gaseous discharge medium 12,said medium 12 producing a copious supply of charges (ions andelectrons) which are alternately collectable on the surfaces of thedielectric members at opposed or facing elemental or discrete areas Xand Y defined by the conductor matrix on nongas-contacting sides of thedielectric members, each dielectric member presenting large open surfaceareas and a plurality of pairs of elemental X and Y areas. While theelectrically operative structural members such as the dielectric members10 and 11 and conductor matrixes l3 and 14 are all relatively thin(being exaggerated in thickness in the drawings) they are formed on andsupported by rigid nonconductive support members 16 and 17 respectively.Preferably, one or both of nonconductive support members 16 and 17 passlight produced by discharge in the elemental gas volumes. Preferably,they are transparent glass members and these members essentially definethe overall thickness and strength of the panel. For example, thethickness of gas layer 12 as determined by spacer 15 is under 10 milsand preferably about 5 to 6 mils, dielectric layers 10 and 11 (over theconductors at the elemental or discrete X and Y areas) is between 1 and2 mils thick, and conductors 13 and 14 about 8,000 angstroms thick (tinoxide). However, support .members 16 and 17 are much thicker(particularly larger panels) so as to provide as much ruggedness as maybe desired to compensate for stresses in the panel. Support members 16and 17 also serve as heat sinks for heat generated by discharges andthus minimize the effect of temperature on operation of the device. Ifit is desired that only the memory function be utilized, then none ofthe members need be transparent to light although for purposes describedlater herein it is preferred that one of the support members and membersformed thereon be transparent to or pass ultraviolet radiation.

Except for being nonconductive or good insulators the electricalproperties of support members 16 and 17 are not critical. The mainfunction of support members 16" and 17 is to provide mechanical supportand strength for the entire panel, particularly with respect to pressuredifferential acting on the panel and thermal shock. As noted earlier,they should have thermal expansion characteristics substantiallymatching the thermal expansion characteristics of dielectric layers 10and 11. Ordinary one-fourth inch commercial grade soda lime plateglasses have been used for this purpose. Other glasses such as lowexpansion glasses or transparent devitrified glasses can be usedprovided they can withstand processing and have expansioncharacteristics substantially matching expansion characteristics of thedielectric coatings 10 and 11. For given pressure differentials andthickness of plates the stress and deflection of plates may bedetermined by following standard stress and strain formulas (see R. J.Roark, Formulas for Stress and Strain, McGrawHiIl, I954).

Spacer 15 may be made of the same glass material as dielectric films l0and 11 and may be an integral rib formed on one of the dielectricmembers and fused to the other members to form a bakeable hermetic sealenclosing and confining the ionizable gas volume 12. However, a separatefinal hermetic seal may be effected by a high strength devitrified glasssealant 15S. Tubulation 18 is provided for exhausting the space betweendielectric members 10 and 11 and filling that space with the volume ofionizable gas. For large panels small bead like solder glass spacerssuch as shown at 158 may be located between conductors intersections andfused to dielectric members 10 and 11 to aid in withstanding stress onthe panel and maintain uniformity of thickness of gas volume 12.

Conductor arrays 13 and 14 may be formed on support members 16 and 17bya number of well known processes, such as photoetching, vacuumdeposition, stencil stressing, etc. In the panel shown in FIG. 4, thecenter spacing of conductors in the respective arrays is about 30 mils.Transparent or semitransparent conductive material such as tin oxide,gold or aluminum can be used to form the conductor arrays and shouldhave a resistance less than 3,000 ohms per line. It is important toselect a conductor material that is not attacked during processing bythe dielectric material.

It will be appreciated that conductor arrays 13 and 14 may be wires orfilaments of copper, gold, silver or aluminum or any other conductivemetal or material. For example, 1 mil wire filaments are commerciallyavailable and may be used in the invention. However, formed in situconductor arrays are preferred since they may be more easily anduniformly placed on and adhered to the support plates 16 and 17.

Dielectric layer members 10 and 11 are formed of an inorganic materialand are preferably formed in situ as an adherent film or coating whichis not chemically or physically efiected during bake-out of the panel.One such material is a solder glass such as Kimble SG-68 manufactured byand commercially available from the assignee of the present invention.

This glass has thermal expansion characteristics substantially matchingthe thermal expansion characteristics of certain soda-lime glasses, andcan be used as the dielectric layer when the support members 16 and 17are soda-lime glass plates. Dielectric layers 10 and 11 must be smoothand have a dielectric strength of about 1,000 v. and be electricallyhomogeneous on a microscopic scale (e.g., no cracks, bubbles, crystals,dirt, surface films, etc.). In addition, the surfaces of dielectriclayers 10 and 11 should be good photoemitters of electrons in a bakedout condition. However, a supply of free electrons for conditioning gas12 for the ionization process may be provided by inclusion of aradioactive material within the glass or gas space. A preferred range ofthickness of dielectric layers 11) and 11 overlying the conductor arrays13 and 14 is between 1 and 2 mils. Of course, for an optical display atleast one of dielectric layers and 11 should pass light generated ondischarge and be transparent or translucent and, preferably, both layersare optically transparent.

The preferred spacing between surfaces of the dielectric films is about5 to 6 mils with conductor arrays 13 and 14 having center to centerspacing of about mils.

The ends of conductors 14-1 141-4 and support member 17 extend beyondthe enclosed gas volume 12 and are exposed for the purpose of makingelectrical connection to interface and addressing circuitry 19.Likewise, the ends of conductors 13-1 13-4 on support member 16 extendbeyond the enclosed gas volume 12 and are exposed for the purpose ofmaking electrical connection to interface and addressing circuitry 19.

As in known display systems, the interface and addressing circuitry orsystem 19 may be relatively inexpensive line scan systems or thesomewhat more expensive high speed random access systems. However, it isto be noted that a lower amplitude of operating potentials helps toreduce problemsassociated with the interface circuitry between theaddressing system and the display/memory panel per se. Thus, byproviding a panel having greater uniformity in the dischargecharacteristics throughout the panel, tolerances and operatingcharacteristics of the panel with which the interfacing circuitrycooperate, are made less rigid.

One mode of initiating operation of the panel will be described withreference to FIG. 3, which illustrates the condition of one elementalgas volume 30 having an elemental cross-sectional area and volume whichis quite small relative to the entire volume and cross-sectional area ofgas 12. The cross-sectional area of volume 311 is defined by theoverlapping common elemental areas of the conductor arrays and thevolume is equal to the product of the distance between the dielectricsurfaces and the elemental area. It is apparent that if the conductorarrays are uniform and linear and are orthogonally (at right angles toeach other) related each of elemental areas X and Y will be squares andif conductors of one conductor array are wider than conductors of theother conductor array, said areas will be rectangles. 1f the conductorarrays are at transverse angles relative to each other, other than 90,the areas will be diamond shaped so that the cross-sectional shape ofeach volume is determined solely in the first instance by the shape ofthe common area of overlap between conductors in the conductor arrays 13and 14. The dotted lines 30 are imaginary lines to show a boundary ofone elemental volume about the center of which each elemental dischargetakes place. As described earlier herein, it is known that thecross-sectional area of the discharge in a gas is affected by, interalia, the pressure of the gas, such that, if desired, the discharge mayeven be constricted to within an area smaller than the area of conductoroverlap. By utilization of this phenomena, the light production may beconfined or resolved substantially to the area of the elementalcross-sectional area defined by conductor overlap. Moreover, byoperating at such pressure charges (ions and electrons) produced ondischarge are laterally confined so as to not materially affectoperation of adjacent elemental discharge volumes.

In the instant shown in FIG. 3, a conditioning discharge about thecenter of elemental volume 30 has been initiated by application toconductor 13-1 and conductor 14-1 firing potential V, as derived from asource 35 of variable phase, for example, and source 36 of sustainingpotential V (which may be a sine wave, for example). The potential V, isadded to the sustaining potential V, as sustaining potential V,increases in magnitude to initiate the conditioning discharge about thecenter of elemental volume 30 shown in F110. 3. There, the phase of thesource 35 of potential V has been adjusted into adding relation to thealternating voltage from the source 36 of sustaining voltage V, toprovide a voltage V,, when switch 33 has been closed, to conductors 13-1and 14-1 defining elementary gas volume 30 sufficient (in time and/ormagnitude) to produce a light generating discharge centered aboutdiscrete elemental gas volume 30. At the instant shown, since conductor13-1 is positive, electrons 32 have collected on and are moving to anelemental area of dielectric member 10 substantially corresponding tothe area of elemental gas volume 30 and the less mobile positive ions 31are beginning to collect on the opposed elemental area of dielectricmember 11 since it is negative. As these charges build up, theyconstitute a back voltage opposed to the voltage applied to conductors13-1 and 141-1 and serve to terminate the discharge in elemental gasvolume 30 for the remainder of a half cycle.

During the discharge about the center of elemental gas volume 30,photons are produced which are free to move or pass through gas medium12, as indicated by arrows 37, to strike or impact remote surface areasof photoemissive dielectric members 10 and 11, causing such remote areasto release electrons 38. Electrons 38 are, in effect, free electrons ingas medium 12 and condition each other discrete elemental gas volume foroperation at a lower firing potential V, which is lower in magnitudethan the firing potential V for the initial discharge about the centerof elemental volume 30 and this voltage is substantially uniform foreach other elemental gas volume.

Thus, elimination of physical obstructions or barriers between discreteelemental volumes, permits photons to travel via the space occupied bythe gas medium 12 to impact remote surface areas of dielectric members111 and 11 and provides a mechanism for supplying free electrons to allelemental gas volumes, thereby conditioning all discrete elemental gasvolumes for subsequent discharges, respectively, at a uniform lowerapplied potential. While in FIG. 3, a single elemental volume 30 isshown, it will be appreciated that an entire row (or column) ofelemental gas volumes may be maintained in a fired condition duringnormal operation of the device with the light produced thereby beingmasked or blocked off from the normal viewing area and not used fordisplay purposes. It can be expected that in some applications therewill always be at least one elemental volume in a fired condition andproducing light in a panel, and in such application it is not necessaryto provide separate discharge of generation of photons for purposesdescribed earlier.

However, as described earlier, the entire gas volume can be conditionedfor operation at uniform firing potentials byuse of extemal or internalradiation so that there will be no need for a separate source of higherpotential for initiating an initial discharge. Thus, by radiating thepanel with ultraviolet radiation or by inclusion of a radioactivematerial within the glass materials or gas space, all discharge volumescan be operated at uniform potentials from addressing and interfacecircuit 19.

Since each discharge is terminated upon a build up or storage of chargesat opposed pairs of elemental areas, the light produced is likewiseterminated. In fact, light production lasts for only a small fraction ora half cycle of applied alternating potential and depending on designparameters, is in the nanosecond range.

After the initial firing or discharge of discrete elemental gas volume30 by a firing potential V;, switch 33 may be opened so that only thesustaining voltage V, from source 36 is applied to conductors 13-1 and14-1. Due to the storage of charges (e.g., the memory) at the opposedelemental areas X and Y, the elemental gas volume 30 will dischargeagain at or near the peak of negative half cycles of sustaining voltageV, to again produce a momentary pulse of light. At this time, due toreversal of field direction, electrons 32 will collect on and be storedon elemental surface area Y of dielectric member 11 and positive ions 31will collect and be stored on elemental surface area X of dielectricmember 10. After a few cycles of sustaining voltage V,,, the times ofdischarges become symmetrically located with respect to the wave form ofsustaining voltage V,,. At remote elemental volumes, as for example, theelemental volumes defined by conductor 14-1 with conductors 13-2 and13-3, a uniform magnitude or potential V from source 60 is selectivelyadded by one or both of switches 34-2 or 34-3 to the sustaining voltageV,,, shown as 36' to fire one or both of these elemental dischargevolumes. Due to the presence of free electrons produced as a result ofthe discharge centered about elemental volume 30, each of these remotediscrete elemental volumes have been conditioned for operation atuniform firing potential V In order to turn off" an elemental gas volume(i.e., terminate a sequence of discharge representing the on" state),the sustaining voltage may be removed. However, since this would alsoturn off" other elemental volumes along a row or column, it is preferredthat the volumes be selectively turned off by application to selected onelemental volumes a voltage which can neutralize the charges stored atthe pairs of opposed elemental areas.

This can be accomplished in a number of ways, as for example, varyingthe phase or time position of the potential from source 60 to where thatvoltage combined with the potential form source 36 falls substantiallybelow the sustaining voltage.

It is apparent that the plates 16-17 need not be flat but may becurved,'curvature of facing surfaces of each plate being complementaryto each other. While the preferred conductor arrangement is of thecrossed grid type as shown, herein, it is likewise apparent that wherean infinite variety of two dimensional display patterns are notnecessary, as where specific standarized visual shapes (e.g. numerals,letters, words, etc.) are to be formed and image resolution is notcritical, the conductors may be shaped accordingly.

The device shown in FIG. 4 is a panel having a large I number ofelemental volumes similar to elemental volume30 (FIG. 3). In this casemore room is provided to make electrical connection to the conductorarrays 13' and 14', respectively, by extending the surfaces of supportmembers 16' and 17 beyond seal 15S, alternate conductors being extendedon alternate sides. Conductor arrays 13' and 14 as well as supportmembers 16' and 17' are transparent. The dielectric coatings are notshown in FIG. 4 but are likewise transparent so that the panel may beviewed from either side.

In accordance with this invention, a latent or visual imageis generatedand recorded from a multiple gaseous discharge panel by projectingthrough a focusing lens 101 latent or visual image radiation from thegaseous discharges of the panel onto the surface of a photosensitivematerial 102 as shown diagrammatically in FIG. 5 adapted to receive andrecord the image. It is contemplated that such projected radiation maybe visible or invisible relative to the human eye; that is, the image asprojected, received, recorded, and/or displayed may be any visible orinvisible representation, likeness, copy, facsimile, etc., of theinformation represented by the gaseous discharge units.

As used herein, photosensitive surface is intended to include any planeor solid body of any suitable geometric shape, which plane or body iscapable of receiving and recording the image radiation from the gaseousdischarge. Also as used herein, recording is intended to include thestoring, registering, duplicating, etc., of information in eithervisible or latent form corresponding to the projected image radiation.Such recording (or storing) can either be directly by the receivingsurface or else modulated by such surface for recording or storing by asecond surface member.

In the broad practice hereof, it is contemplated using a wide variety ofmaterials and/or processes as the photosensitive surface.

In one specific embodiment, there is used a photoconductive insulatingmaterial capable of receiving and storing an image by means ofpersistent internal polarization.

Persistent internal polarization (abbreviated herein as PIP) involvesthe separation of positive and negative charges in a photoconductiveinsulating material by simultaneous irradiation and the application ofan electric field. The charges are subsequently trapped and remain fixedor frozen in the photoconductor for a finite time to form an internalpolarization field. This process and the theory thereof are well knownin the art. See, for example, Electrophography by R. M. Schaffert, TheFocal Press, London and New York (1965), pages 59-77, and PersistentInternal Polarization by Kallmann and Rosenberg, The Physical Review,vol. 97, No. 5 (Mar. 15, 1955), pages l,596-1,6l0, both of which areincorporated herein by reference.

In this embodiment, the photosensitive surface is constructed out of amaterial capable of developing PIP when simultaneously exposed toirradiation from the gaseous discharge units and an electric field suchthat the panel image radiation is stored as a latent image via frozen ortrapped charges within the PIP material. The latent image can be madeinto a visible image including hardcopy readout by means of a toner andtoner receiving surface appropriately applied to the PIP surface, suchPIP image development process being well known in the art.

The phenomenon of PIP can be achieved in any material which exhibits thefollowing characteristics;

l. The material must have a high resistivity in the 7 dark (a lowdensity of free chargeslwhereby it is a good insulator in the absence ofpenetrating radiations such as light or high energy particles.

2. The material must be photoconductive; that is, it

must have decreased resistivity when penetrated sulfide, zinc selenide,cadmium selenide, zinc oxide,

cadmium oxide, selenium, tellurium, anthracene, chrysene, alkaline earthhalides, and mixtures of same, especially mixtures of selenium withtellurium, zinccadmium selenides, and zinc-cadmium sulfides. It is alsocontemplated that a small effective amount of a suitable activator, e.g.gold, silver, or copper, may be incorporated with the photoconductingPIP substance.

The commonly used powdered PIP materials are typically dispersed ormixed with a suitable resin binder such as a cellulose acetate, ether,or ester, silicones, vinyl resins, and/or epoxy resins.

In still another specific embodiment of this invention, thephotosensitive receiving and recording surface comprises an ELECTROFAXprocess wherein there is used photoconductive pigment such as zinc oxideon a substrate such as a paper. This process differs from the PIP inthat the panel image is directly reproduced on the photoconductivecoated substrate and it does not have to be transferred to anothersurface. Likewise, it has the advantage that sensitized ELECTROFAX papermay be combined with negatively charged toner to give dark or lightcopy.

Another specific embodiment comprises the use of xerography, such asdescribed in Xerography and Related Processes by John H. Dessauer andHarold E. Clark, Xerox Corporation, 1965, Focal Press.

In still a further embodiment hereof, there is used a i system havingthe advantage of negative working, said system comprising image wisecharge deposition onto a dielectric coated paper through aphotoconductor sensitive to the radiation from the gaseous discharges.Such a system is described in US. Letters Patent 3,502,408.

This invention has several highly important advantages includingphotosensitive recording of an image from one side of a gaseousdischarge panel while the image is being displayed and/or viewed fromthe other panel side without the use of mirrors.

Another most important advantage is that the image radiation emissioncan be different (if needed) for recording and for viewing, e.g. by theuse of luminescent phosphors and various gaseous medium mixtures.-

I claim:

1. In the operationv of .an apparatus comprising in combination agaseous discharge display/memory panel and an image recording device,said panel being characterized by an ionizable gaseous medium in a gaschamber formed by a pair of dielectric material members having opposedcharge storage surfaces, which dielectric material members are capableof transmitting light therethrough and are respectively backed by aseries of parallel-like electrode members, the electrode members behindeach dielectric material member being transversely oriented with respectto the electrode members behind the opposing dielectric material memberso as to define a plurality of discrete discharge volumes, each of whichconstitutes a discharge unit, and wherein the gas is selectively ionizedwithin each discharge unit by operating voltages applied to thetransversely oriented electrode members, said image recording devicebeing characterized by a photosensitive surface facing one of saiddielectric material members for directly receiving and recording animage, the improvement which comprises generating an image comprised ofone or more gaseous discharge units and then projecting image radiationfrom the discharge units in opposite directions through both saiddielectric material members, said image radiation projected through saidone dielectric material member being directly received and recorded onsaid photosensitive surface, whereby said image may be simultaneouslyobserved directly through the other of said dielectric material memberswhile it is being directly received and recorded on said photosensitivesurface.

2. The improvement of claim 1 wherein the photosensitive surface isconstructed out of a PIP material.

3. The improvement of claim 1 wherein the photosensitive surfacecomprises an ELECTROFAX system of photoconductive pigment on asubstrate.

4. The improvement of claim 3 wherein the pigment is zinc oxide and thesubstrate is paper.

5. An image display and recording apparatus adapted to simultaneouslydisplay and record an image comprising in combination a gaseousdischarge display/memory panel and an image recording device, said panelcomprising an ionizable gaseous medium in a gas chamber formed by a pairof dielectric material members having opposed charge storage surfaces,which dielectric material members are capable of transmitting lighttherethrough and are respectively backed by a series of parallel-likeelectrode members, the electrode members behind each dielectric materialmember being transversely oriented with respect to the electrode membersbehind the opposing dielectric material member so as to define aplurality of discrete discharge volumes, each of which constitutes adischarge unit, and means for selectively applying operating voltages tosaid transversely oriented electrode members for selectively ionizingsaid discharge units for generating an image which is radiated inopposite directions through both said dielectric material members, andsaid image recording device including a photosensitive surface facingone of said dielectric material members for directly receiving andrecording the image radiated from said discharge units through said onedielectric material member, whereby said image may be simultaneouslyobserved directly through the other of said dielectric material membersand directly received and recorded on said photosensitive surface.

6. The invention of claim 5 wherein the photosensitive surface isconstructed out of a PIP material.

7. The invention of claim 5 wherein the photosensitive surface comprisesan ELECTROFAX system of photoconductive pigment on a substrate.

8. The invention of claim 7 wherein the pigment is zinc oxide and thesubstrate is paper.

9. An image display and recording apparatus adapted to simultaneouslydisplay and record an image comprising in combination a gaseousdischarge display/memory panel and an image recording device, said panelcomprising a pair of spaced-apart non-conductive support members, a pairof conductor arrays arranged one on each of the confronting surfaces ofsaid support members, the arrays being in transverse relativeorientation so as to provide a series of cross-points therebetween, eachdefining a discharge unit, a thin dielectric oriented electrode membersfor selectively ionizing said discharge units for generating an imagewhich is radiated in opposite directions through both said dielectricmaterial coatings and support members; and said image recording deviceincluding a photosensitive surface facing one of said support membersfor directly receiving and recording the image radiated from saiddischarge units through said one support member whereby said image maybe simultaneously directly observed through the other of said supportmembers and directly received and recorded on said photosensitivesurface.

10. The invention of claim 9 wherein the photosensitive surface isconstructed out of a PIP material.

11. The invention of claim 9 wherein the photosensitive surfacecomprises an ELECT ROFAX system of photoconductive pigment on asubstrate.

12. The invention of claim 11 wherein the pigment is zinc oxide and thesubstrate is paper.

